The aim of this research is to investigate the role played by two TGF& related polypeptides, TGF(Beta 2) and Vg-r, in the growth and differentiation of the mouse embryo. The first part of the proposal is designed to follow the expression of TGF(BETA 2) in mouse embryos using Northern analysis and in situ hybridization. Initially, a variety of tissues and organs will be studied at different stages of development. Selected examples will then be examined in more detail, in order to correlate expression with rapid proliferation, differentiation, morphogenesis or embryonic induction. Evidence for expression will also be sought in differentiating teratocarcinoma and ES stem cells, and the effect of the purified protein on these cells and cultured early embryos will be investigated. The goal of the second part of the proposal is to characterize mouse genes related to the Xenopus Vg1 gene, which encodes a maternal mRNA progressively localized to the vegetal pole of the amphibian embryo. One such cDNA, designed Vg-r has already been isolated and sequenced and will be used to isolate related genes by further screening of both mouse genomic and cDNA libraries at low stringency. The expression of the mouse Vg1 related gene(s) will be followed using Northern analysis, in situ hybridization, and antibodies raised against predicted protein sequence (peptides) and/or fusion protein produced in bacteria. Finally, a long term goal will be to study the in vivo function of the Vg-r gene during development. One strategy will be to misregulate Vg-r expression is transgenic mice. Another will be to block its expression by homologous recombination with a manipulated DNA sequence in embryonic stem (ES) cells, followed by transmission of the defective (null) gene through the mouse germ line.